The maker of osteoporosis drug Prolia and Enbrel for rheumatoid arthritis and skin disorders said second-quarter net income was $1.26 billion, or $1.65 per share, down from $1.27 billion, or $1.61 per share, a year earlier.

Excluding one-time items, Amgen said adjusted net income was $1.44 billion, or $1.89 per share, well above the $1.74 analysts were expecting.

Amgen's stock fell $1.80, or 1.6 percent, to $109.40 in after-hours trading, giving back most of the $1.83 it gained during the regular trading session.

"We saw solid product trends during the second quarter and are carrying good momentum into the second half," CEO Robert A. Bradway said in a statement. "We continue to make excellent progress with our pipeline of innovative" experimental drugs.

Sales were led Neulasta and Neupogen, for fighting infection in cancer patients, with their combined sales up 7 percent to $1.44 billion. Enbrel sales jumped 9 percent to $1.16 billion, but sales of anemia drug Aranesp slipped 2 percent to $524 million.

Two newer drugs, Prolia and Xgeva for preventing skeletal damage from solid tumors, saw their combined sales jump 46 percent, to $437 million. They contain the same active ingredient, but at different doses.

Amgen raised its 2013 profit forecast to $7.30 to $7.45 per share, from the $7.05 to $7.35 per share it predicted in April. It also tweaked its revenue forecast, saying it now expects "the upper end" of its January forecast of $17.8 billion to $18.2 billion in sales for the full year.